It really depends on the horse and your personal preference. I use hackamores on all my horses just because that's what's we have always used.
I've heard people saying they use them because they don't want to jerk on the horses mouth, that may be true but I think it's important to note that a rough rider can hurt a horse in a hackamore or other bitless bridle just as easy as they could with a bit. I've heard of rare (thankfully) cases where riders have crushed the nasal cavity from being so rough.
Obviously I'm sure you wouldn't be that rough with your horses but bitless bridles in my opinion, are just as effective as bits, you just have to keep in mind that what may work for one horse may be a disaster for another.
When riding my horse I no longer have my heart in my chest, but between my knees.